Devices for venting fuel tanks in vehicles and, in particular, marine vessels, are well known in the art. Typical marine fuel venting devices facilitate the process of filling a tank with liquid fuel by compensating for changes in pressure within the tank as the volume of fuel dispensed into the tank increases and the fuel transitions between liquid and gas phases. Such devices typically consist of vent lines installed in the tanks. One end of the vent line is formed into the top of the tank and the other end opens into the atmosphere exterior to the tank.
Although a vent line helps prevent the buildup of fuel pressure within the tank, the vent line does not prevent the unintentional overboard venting of liquid fuel through the vent line, which frequently occurs when a marine fuel tank is being refueled. This unintentional venting occurs when the tank is overfilled or becomes full and resultant displaced vapors carry liquid fuel through the vent line to be discharged into the water or onto land.